Acoustooptic

Acoustooptic refers to phenomena and devices that use the interaction between sound waves and light in a medium to modulate, deflect, or frequency-shift light. The effect arises when a traveling acoustic wave induces a moving refractive-index grating in the material via the photoelastic effect, creating a dynamic Bragg grating that diffracts light.

In a typical acousto-optic modulator or deflector, a radio-frequency signal drives a piezoelectric transducer attached to a crystal (such as TeO2, LiNbO3, GaP, or fused silica). The induced acoustic wave forms a phase grating; light diffracts into one or more orders, with the first-order beam shifted in frequency by the acoustic frequency and deflected by an angle that satisfies the Bragg condition. The diffraction efficiency depends on the optical wavelength, material photoelastic coefficients, acoustic power, interaction length, and polarization. Higher RF power increases efficiency but also raises loss and heating.

Common devices include acousto-optic modulators (AOMs), which control optical intensity or frequency; acousto-optic deflectors (AODs), which steer beams rapidly; and acousto-optic tunable filters (AOTFs), which select wavelengths with a fixed acoustic frequency and polarization.

Applications span laser scanning, fiber-optic communications, spectroscopy, and imaging. They are valued for fast, solid-state, non-mechanical control, though efficiency, bandwidth, and thermal management depend on material choice and operating conditions.